The best abdominal exercise to both strengthen your core and firm your waist shortens the fibers in the front and sides of the abdominal wall. The reverse plank is not a sophisticated exercise, and it needs no specialized equipment, so it is sometimes an ignored exercise for the core. However, it hits postural back muscles and even the glutes and hamstrings while also strongly engaging and shortening the muscles of the abdominal wall.

Importantly, if you are committed to tightening your abs, you should raise the aerobic plan in your workout to twice each day if possible. That does not mean you need to live in the gym, as the second aerobic piece could be a brisk 30- to 40-minute walk in the evening.

Exercise: Reverse Planks
1. Sit on the floor with your hips flexed and with your legs extended in front of you, and your knees straight.

2. Put the palms of your hands on the floor and spread your fingers out for a good base of support. Lean backward so that your torso forms about a 45-degree angle with the floor. At this angle your hands should be behind your hip joints approximately straight down from your shoulders.

3. Support your weight on your heels and hands and lift your hips and body upward toward the ceiling.

4. Continue lifting until your torso, thighs and legs form a straight line.

5. Tighten your abdomen and pull in on your abdomen as you lift upward, with the idea that you are trying to pull your abdomen inward toward your spine.

6. Try to hold the straight line position beginning at 15 seconds and working up to 30 seconds.

7. Reverse the lift by flexing the hips and lowering them back to the floor.

8. As soon as your buttocks touch the floor, begin the next lift upward.

If your hips start to drop, rather than holding the straight line position, drop down, rest briefly, then start the next repetition. It is preferable to hold the straight line position for a shorter time than to attempt to lose the straight line and hold on for a longer period in an incorrect position.

The reverse plank exercise is effective but it is not terribly difficult to perform, especially once you get the feel of holding your body in a straight line. A lot of muscles are active, but your abdomen, hips and glutes will really tighten and firm when you use reverse planks. If you increase the frequency of your aerobics, and use reverse planks as part of your regular core and abdominal training (maybe even a few sets at home between workouts), you’ll soon reveal new flat and firm abdomen and firmer glutes.